Improvement in the mildfactube of soda and potash



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Letters Patent No. 78,375, dated ilfay 26, 1868.

IMPROVEMENT IN THE MANUFACTURE OF SODA AND POTASH.

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TO ALL WHOM IT MAY CONCERN:

Be itknown that I, A. G. HUNTER, of Flint,'Wales, temporarily residingin Fairliaven, in the county. of

New Haven, and State of Connecticut, have invented a new Improvcment inhiianufaetureof Soda and Potash; and I do hereby declare the followingto be a full, clear, and exact description of the same. i

The object of this, invention is to efiect the conversion of silicate ofsoda or silicate of potash into the corresponding carbonated alkali, bymeans of bicarbonate "of lime, that is, carbonate of lime dissolved byan excess of'carbonic acid.

v I effect this by mixing the alkaline silicate to be treated with asolution of bicarbonate of lime, whereby silicate .of lime and alkalinebicarbonate are produced. This double decomposition may be effected atordinary temperatures, and is facilitatedwhen performed in contact withcarbonic acid. The solution of bicarbonate of lime may, be prepared byacting on lime or carbonate of lime suspended in water by carbonic acid.7

Several forms of apparatus may be employed t o carry out this invention.Among others I may mention- First, open tanks or vessels,'provided withagitators, toefiect the suspension, in water, of the lime or carbonz rteof lime, while being, dissolved bycarbonic acid brought in contact withthe'liquid, and to effect a thorough mixture of the alkaline silicate tobe treated, (which is most conveniently added as a solutioin) with thesolution ofbicarbonateof lime, and subsequently, when the precipitatedsilicate of lime has settled, and the solution of alkalinecarbonate hasbeen run oil therefrom, to wash the said silicate of lime free fromadhering alkaline salts.

The carbonic acid may bederived'from several sources, among others, fromburning coal, or from a limekiln, and may be brought in contact with theliquid by a draught, or by a fan,or injected into the liquid by Second,a tower, provided with shelves or diaphragms, placed at a slightinclination, and so arranged that the lime or carbonate-of-limeliquor,when introduced on the top shelf of the tower shall, in flowingdownwards. from shelf to shelfi-describc a zigzag course from sidetoside of the tower, while the carbonic-acid gas, being admitted at the.bottom oi'the towonascends and meets, the descending-liquid, andconverts the lime carbonate of limeinto' bicarbonate of lime, which maythen 'be'used to'decoinpose the alkaline silicate. 1

Third, closed tanks 6r vessels capable of standing pressure, andprovided with agitators and suitable inlets and outlets, in which thesolution of bicarbonate of lime may be prepared under pressure, and thedecomposition of the alkaline silicate to betreated also effected underpressure produced by injection of carbonic acid." In using this form ofapparatus, the alkaline-silicate may be pumped in as a solution, or itmay be placed in the apparatus at the same timeas the lime or carbonateof lime and water are, and the whole agitated, together with injectionof. carbonic. acid, till it is found, by testing a sample obtained by agauge-cock, that thealkaline silicate is converted into carbonate. Whenthis point is reached, the injection of carbonic acid and the agitatorare stopped, the silicate of lime allowed to settle, the solution ofalkaline carbonate subsequently run of, and the residuary silicate oflime washedwith water, to'free it of alkaline salts. By this form ofapparatus, more conccntrated solutions may be obtained than in openvessels, and the greater the pressure, the more concentrated solutionmay beobtained. i i v The silicate of lime may be used for glass-making,and the solutions of carbonated alkali may either be used as such, or byconcentration at low temperature or in name may 'be obtained as alkalinebicarbonate, (vacuum-. pans, such as sugar-rcfiners use, may be hereadvantageously employed,) or by concentration byboiling'may be obtainedas crystallized carbonated alkali,or, by boiling to dryness, as drycarbonated alkali, or, if causticized by l'ime,-may-be obtained ascaustic alkali. The respective modes of such concentration, evaporation,or causticizing are well known to practical chemists.

The respective quantities of bicarbonate ofliinc, and of the alkalinesilicate to be treated, are determined 7 by their equivalents, which arewell known to chemists.

Having thus fully described myinvention, what I claim as new, and desireto secure by Letters Patent, is

The process of converting silicateof soda or silicate of'potash into"the cm'respondiug carbonate, by'double decomposition with bicarbonateof lime, as substantially described herein.

A. G. HUNTER.

Witnesses:

J. H. SHUMWAY, A. J. TIBBITS.

